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Cerebral Abscess

Summary

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  • Focal, purulent infection within the brain parenchyma
  • Typically presents with headache, fever, and focal neurological deficits
  • Imaging shows ring-enhancing lesion with surrounding oedema on CT/MRI1

Pathophysiology

  • Caused by bacterial, fungal, or parasitic infections
  • Three main routes of infection:
    • Hematogenous spread (30-40%)
    • Direct extension from contiguous infections (20-30%)
    • Post-traumatic or post-surgical (10-15%)
  • Progression through four stages:
    1. Early cerebritis (1-3 days)
    2. Late cerebritis (4-9 days)
    3. Early capsule formation (10-13 days)
    4. Late capsule formation (>14 days)

Demographics

  • Incidence: 0.3-1.3 per 100,000 person-years
  • More common in males (2:1 male-to-female ratio)
  • Peak incidence in third and fourth decades of life
  • Risk factors:
    • Immunosuppression
    • Congenital heart disease
    • Chronic otitis media or sinusitis
    • Dental infections
    • Neurosurgical procedures

Diagnosis

  • Clinical presentation:
    • Headache (70-90%)
    • Fever (45-70%)
    • Focal neurological deficits (50-65%)
    • Altered mental status (30-60%)
    • Seizures (25-35%)
  • Laboratory findings:
    • Elevated white blood cell count
    • Elevated C-reactive protein and erythrocyte sedimentation rate
  • Lumbar puncture generally contraindicated due to risk of herniation
  • Definitive diagnosis: culture of abscess contents

Imaging

  • CT:
    • Early stages: Ill-defined, low-density area with patchy enhancement
    • Late stages: Well-defined, ring-enhancing lesion with surrounding oedema
    • "Double ring sign": Hypodense centre with hyperdense rim and thin hypodense outer layer
  • MRI:
    • T1-weighted: Hypointense centre with isointense to hyperintense rim
    • T2-weighted: Hyperintense centre with hypointense rim
    • DWI: Restricted diffusion in abscess cavity
    • ADC: Low values in abscess cavity
    • Contrast-enhanced: Ring enhancement with surrounding oedema
  • Advanced techniques:
    • MR spectroscopy: Elevated lactate, lipids, and amino acids
    • Perfusion imaging: Low relative cerebral blood volume in abscess cavity

panels-1

  • A 50-year-old patient presented with a three-day history of fevers after a tonic-clonic seizure (three months after extensive dental work).
  • Imaging showed many ring-enhancing lesions, with central diffusion restriction, surrounded by vasogenic oedema.

Treatment

  • Prolonged targeted antibiotics with stereotactic aspiration or excision for larger lesions
  • Serial imaging to confirm resolution

Differential diagnosis

Differential Diagnosis Differentiating Feature
Glioblastoma Irregular ring enhancement on contrast-enhanced MRI; less restricted diffusion on DWI
Metastatic brain tumour Multiple lesions; known primary cancer; smoother enhancement ring
Cerebral infarction Follows vascular territory; no ring enhancement in acute phase
Toxoplasmosis Multiple small lesions; HIV or immunocompromised status; positive serology
Tuberculoma Solid nodular enhancement; concurrent pulmonary findings; positive TB tests
Demyelinating lesion Incomplete ring sign; periventricular white matter involvement
Neurocysticercosis Multiple cystic lesions; calcifications; travel history to endemic areas
Fungal infection Irregular thick-walled lesions; immunocompromised status; CSF fungal culture
Subacute haematoma Haemosiderin rim on T2*; history of trauma or coagulopathy
Radiation necrosis History of radiation therapy; delayed onset after treatment

  1. Cossu et al. Cerebral abscess after neuro-vascular embolization: Own experience and review of the literature. 2017. Acta neurochirurgica - Open in new tab. ↩